I had my local shop install mine but watched a bit as they worked and am pretty sure they didn't remove the wheels. I seem to remember them jacking up the rear to let the wheels hang so they could get as much working space as possible. I have two air fittings but can't really see why I'd ever need different pressure in either side. You'll love these bags. Other than the 5th I've never really maxed out my current ones on my Hemi. On my old Dmax I had the same Firestone's and loaded that truck with all kinds of crazy stuff - 3000# of sheetrock, a yard+ of gravel, etc. With enough air you can pretty much prevent your truck from sagging at all if you don't want it to.